A. Field of the Invention
The present invention relates to a fluid changing device for changing a channel in an endoscope, thereby regulating the flow of a fluid in the channel.
B. Description of the Prior Art
(a) Generally known as an example of a conventional endoscopic fluid changing device is a suction adjusting device which is disclosed in Japanese Utility Model Publication No. 56-9441. This device is built in an opening portion of an endoscope, in which a medical instrument is to be inserted. In this suction adjusting device, a cylindrical casing is fluidly connected to an instrument channel, and a suction port, connecting with a suction unit, is formed in the middle portion of the side wall of the casing. An inner cylinder is fixed inside the casing. It contains a slide valve for controlling the suction port. Normally, the valve is open, so that an opening portion of the casing and the suction unit are fluidly connected, thus reducing the load of a suction pump, in the suction unit. In sucking filth or the like from the body cavity, through the instrument channel, an operator closes the opening portion of the casing, with his finger, to effect suction. In feeding a liquid into the body cavity, through the opening portion and the channel, moreover, the slide valve is shifted to close the suction port.
(b) In a suction adjusting device stated in Japanese Utility Model Disclosure No. 60-23001, a valve seat is formed on the bottom portion of a cylindrical casing, and an elastic valve member is disposed in the casing. In feeding a liquid into the body cavity, a passage for suction is closed by means of the elastic valve.
(c) Conventional passage changing means, as stated, for example, in Japanese Patent Disclosure No. 57-103621, comprises a cylinder with a suction port in its side wall, and a piston with an O-ring thereon. A passage is changed by sliding the piston in the cylinder.
In prior art systems (a) and (b), the operator must close the opening portion (relief port) with his finger, during the suction. Therefore, filth or other matter, sucked from the body cavity through the instrument channel, may possibly reach the relief port, thus soiling the operator's finger. This is not very sanitary.
When the filth or other matter is not expected to be sucked from the body cavity, moreover, it can be sucked little by little, through the instrument channel, although the opening portion of the casing is open. If the endoscope is inserted, for example, in a bronchial tube, therefore, the matter may possibly prevent a patient from breathing well. If the stomach or other internal organ is inflated with air, introduced through the endoscope inserted in the organ, for observation, the air will be able to flow out of the organ, through the opening portion, thereby preventing a satisfactory observation.